Highly recyclable and efficient electrocatalytic synthesis of adipic acid catalyzed by ultra-alkali-resistant [Ni36] nanocages in MOF.

As a pivotal industrial chemical, adipic acid (AA) is synthesizable through the electrocatalytic oxidation of cyclohexanol under ambient conditions, utilizing electrons as a clean oxidant. This approach circumvents the energy-intensive and environmentally detrimental nature of conventional petrochemical processes, thereby offering a sustainable alternative for AA production. However, existing electrocatalysts are often plagued by instability in alkaline media, and their structure-activity relationships remain poorly understood. Here, we report a novel [Ni36] nanocage-based metal-organic framework ([Ni9]-MOF) synthesized via a bottom-up strategy from discrete [Ni9]-clusters, exhibiting excellent stability under both strong alkaline (8 M NaOH) and acidic (1 M HCl) conditions. [Ni9]-MOF demonstrates superior AA production (0.1239 mmol h-1 cm-2 at 1.61 V), and maintains this high activity over 25 cycles with negligible loss, surpassing all prior high-performance catalysts in durability. Mechanistic studies reveal a three-step oxidation pathway via cyclohexanone, 2-hydroxycyclohexanone and 6-hydroxyadipic acid. Density functional theory calculations indicate the MOF framework enhances the charge density at the active [Ni9] site, accelerating reaction kinetics. This work not only provides a rational design strategy for constructing highly stable MOFs, but also presents the first MOF-based electrocatalyst for AA synthesis, opening new avenues for sustainable chemical production under mild conditions.